Evaluation Edition - Evaluation Edition allows you to have 2 administrators in for 30 days. You can manage unlimited resources and evaluate all features of Enterprise Edition. During evaluation you can get free technical assistance.
Free Edition - Download valid for ever, capable for supporting a maximum of 1 administrator. You can manage a maximum of 10 resources and you will all functionalities of Standard Edition.
Registered Version - need to buy license based on the number of administrators required and the type of edition Standard/Premium/Enterprise:
Standard - If your requirement is to have a secure, password repository to store your passwords and selectively share them among enterprise users, Standard Edition would be ideal.
Premium - Apart from storing and sharing your passwords, if you wish to have enterprise-class password management features such as remote password synchronization, password alerts and notifications, application-to-application password management, reports, high-availability and others, Premium edition would be the best choice.
Enterprise - If you require more enterprise-class features like auto discovery of privileged accounts, integration with ticketing systems and SIEM solutions, jump server configuration, application-to-application password management, out-of-the-box compliance reports, SQL server / cluster as backend database, Enterprise edition will be ideal.